This invention relates to an internal combustion engine, especially to a device for controlling the flow in the helical type intake port.
It is well known that a helical type intake port is generally formed with the helical portion around an intake valve and the substantially straight inlet portion tangentially contiguous to the helical portion. When constructing the helical type intake port, the intake port must be formed in such a shape as to cause an increase of the flow resistance in order to get a strong swirl flow in the combustion chamber at a low revolution and low load, thus resulting in a decrease of the volumetric efficiency at a high revolution.